helloweb.go

package main

import (
	"html/template"
	"io/ioutil"
	"net/http"
	"regexp"
)

const (
	templatePath string = "tmpl/"
	dataPath     string = "data/"
)

var (
	templates = template.Must(template.ParseFiles(templatePath+"view.html", templatePath+"edit.html"))
	validPath = regexp.MustCompile("^/(edit|save|view)/([a-zA-Z0-9]+)$")
)

type Page struct {
	Title string
	Body  []byte
}

func (page *Page) save() error {
	filename := page.Title + ".txt"
	return ioutil.WriteFile(dataPath+filename, page.Body, 0600)
}

func load(filename string) (*Page, error) {
	body, err := ioutil.ReadFile(dataPath + filename + ".txt")
	if err != nil {
		return nil, err
	}
	return &Page{Title: filename, Body: body}, nil
}

func rendertmplate(w http.ResponseWriter, tmpl string, p *Page) {
	err := templates.ExecuteTemplate(w, tmpl+".html", p)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

func makeHandler(fn func(http.ResponseWriter, *http.Request, string)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		m := validPath.FindStringSubmatch(r.URL.Path)
		if m == nil || len(m) < 2 {
			http.NotFound(w, r)
			return
		}
		fn(w, r, m[2])
	}
}

func viewHandler(w http.ResponseWriter, r *http.Request, title string) {
	p, err := load(title)
	if err != nil {
		http.Redirect(w, r, "/edit/"+title, http.StatusFound)
		return
	}
	rendertmplate(w, "view", p)
}

func editHandler(w http.ResponseWriter, r *http.Request, title string) {
	p, err := load(title)
	if err != nil {
		p = &Page{Title: title}
	}
	rendertmplate(w, "edit", p)
}

func saveHandler(w http.ResponseWriter, r *http.Request, title string) {
	body := r.FormValue("body")
	p := &Page{Title: title, Body: []byte(body)}
	err := p.save()
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/view/"+title, http.StatusFound)
}

func main2() {
	http.HandleFunc("/view/", makeHandler(viewHandler))
	http.HandleFunc("/edit/", makeHandler(editHandler))
	http.HandleFunc("/save/", makeHandler(saveHandler))
	http.ListenAndServe(":8080", nil)
}